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Temperature Measurement

In the last decades many methods have been developed for measuring temperature. Most of these rely on measuring some physical property of a working material that varies with temperature. One of the most common devices for measuring temperature is the glass thermometer. This consists of a glass tube filled with mercury or some other liquid, which acts as the working fluid. Temperature increases cause the fluid to expand, so the temperature can be determined by measuring the volume of the fluid. Such thermometers are usually calibrated, so that one can read the temperature, simply by observing the level of the fluid in the thermometer.

Other types are based on bi-metals, infrared radiation, thermo-electric voltage measurement or electrical resistance measurement. Since most physical properties are more or less affected by temperature, it is easy to find an appropriate and reliable process for most applications.

Thermistors and RTDs

A thermistor is a type of resistor whose resistance varies with temperature. Thermistors differ from resistance temperature detectors (RTD) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals.

Thermocouples

A thermocouple is a junction between two different metals that produces a voltage related to a temperature difference. Thermocouples are a widely used type of temperature sensor for measurement and control and can be read out by the use of the TMP01 device which features adaptive cold junction compensation.